It is proposed to continue our evaluation of the primary H-ion ejection accompanying electron transport and ATP hydrolysis in the mitochondrial inner membrane, in connection with the mechanism of oxidative phosphorylation, particularly the validity of the chemiosmotic hypothesis. We shall utilize the oxygen pulse, reductant pulse and Ca-ion pulse methods. We also propose to examine the utilization of intramitochondrial ATP for rapid segregation of extramitochondiral Ca2-ion in mitochondria isolated from different tissues, including tumor cells, in connection with the postulated role of mitochondria in the regulation of Ca2-ion-dependent activities in cells. It is also proposed to continue our work on the extraction and purification of the ADP-ATP carrier of the inner mitochondrial membrane and examination of its sensitivity to inhibitors; we also expect to attempt the reconstitution of ADP and ATP transport with a purified carrier embedded in a synthetic phospholipid bilayer in an aperture. The role of mitochondria in the first stages of biological calcification processes is also being examined, with special reference to the identification of enzymatically-formed organic inhibitors of the transition from amorphous tricalcium phosphate to crystalline hydroxyapatite. BIBLIOGRAPHIC REFERENCES: Betts, F., Blumenthal, N.C., Posner, A.S., Decker, G.L. and Lehninger, A.L., The atomic structure of intracellular amorphous calcium phosphate deposits, Proc. Nat. Acad. Sci. 72, 2088 (1975). Jacobus, W.E., Tiozzo, R., Lugli, G., Lehninger, A.L., and Carafoli, E., Aspects of energy-linked calcium accumulation by rat heart mitochondria, J. Biol. Chem. 250, 7863 (1975).